These kits by MadLab are great to get younger kids and even adults into soldering! They are fun, educational and very entertaining!
The Wonky Wire is used to test the steadiness of your hand. It utilizes a circuit with an oscillator that has a very high oscillation frequency of about 3kHz (3000 cycles per second). As you try to trace the outline of the convoluted wire with the loop, the slightest touch will cause a tone to sound. The variable resistor can be used to change the pitch of the tone.